On Wed, Nov 17, 2010 at 01:31, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Well, we're not going to increase the default to gigabytes, but we could
> very probably increase it by a factor of 10 or so without anyone
> squawking. It's been awhile since I heard of anyone trying to run PG in
> 4MB shmmax. How much would a change of that size help?
In my testing, when running a large bulk insert query with fdatasync
on ext4, changing wal_buffers has very little effect:
http://ompldr.org/vNjNiNQ/wal_sync_method1.png
(More details at
http://archives.postgresql.org/pgsql-performance/2010-11/msg00094.php
)
It would take some more testing to say this conclusively, but looking
at the raw data, there only seems to be an effect when moving from 8
to 16MB. Could be different on other file systems though.
Regards,
Marti
